Amphiphilic Comb Polymer Research Articles

Preparation of albumin preferential surfaces on poly(vinyl chloride) membranes via surface self-segregation.

Poly(vinyl chlorides)-graft-[omega-stearyl-poly(ethylene oxide)] (PVC-g-SPEO), which has a poly(vinyl chloride) (PVC) backbone, poly(ethylene oxide) (PEO) side chain, and stearyl end groups, has been synthesized. Self-organizing blends of the amphiphilic comb polymer in poly(vinyl chlorides) have been examined as a means to create albumin preferential surfaces on polymer films. X-ray photoelectron spectroscopy (XPS) analysis indicates substantial surface segregation of the PVC-g-SPEO. A surface concentration of 59.9 EO wt % is achieved by the solution casting and heat treatment of a film with a bulk concentration of only 3.78 EO wt %. In the aqueous environment, the surface rearrangement of PVC-g-SPEO/PVC blend film is limited and presents a high interfacial energy and high depolar component of interfacial energy due to the "tail-like" SPEO side chain. Protein adsorption tests confirm that PVC-g-SPEO/PVC blend films absorb high levels of albumin and dramatically resist fibrinogen adsorption. Surfaces to attract and reversibly bind albumin, which might diminish the occurrence of thrombosis, inflammation, and infection, are developed by self-organizing blends of the amphiphilic comb polymer in poly(vinyl chlorides).

Micropatterns of a Cell-Adhesive Peptide on an Amphiphilic Comb Polymer Film

We report in this paper a generic method to modify the surfaces of common polymeric biomaterials that enables spatially resolved attachment and growth of mammalian cells in a biologically relevant milieu. We demonstrate that an amphiphilic comb polymer presenting short oligoethylene glycol side chains can be coated onto a number of different polymeric biomaterials, namely polystyrene, poly(methyl methacrylate), and poly(ethylene terephthalate) from a methanol/water mixture. The comb polymer film is stable in water and presents reactive COOH groups at the oligoethylene glycol chain ends, thereby permitting the surface of the comb polymer to be patterned with a cell adhesive, arg-gly-asp peptide. The micropatterned surfaces spatially confine the attachment and growth of fibroblasts for ∼24 h in 10% serum to the patterned regions.

Design and performance of foul-resistant poly(vinylidene fluoride) membranes prepared in a single-step by surface segregation

Immersion precipitated membranes with enhanced fouling resistance are prepared from blends of poly(vinylidene fluoride) (PVDF) and a free-radically synthesized amphiphilic comb polymer having a methacrylate backbone and poly(ethylene oxide) side chains. X-ray photoelectron spectroscopy analysis indicates substantial surface segregation of the comb polymer during membrane coagulation, providing an integrated near-surface coverage of up to 50 vol.% comb for a membrane containing 10 wt.% (14.6 vol.%). The surface coverage increases with comb molecular weight, providing hydrophilic surfaces with excellent stability and substantiating a proposed mechanism for surface localization. Separation surface porosities for comb-modified membranes are up to an order of magnitude higher than PVDF controls. With the combined benefits of fouling resistance and increased porosity, a membrane containing 10 wt.% comb is over 20 times as permeable as a PVDF-only membrane with equivalent separation characteristics after 3 h of filtration of a foulant protein solution.

Influence of the alkyl-chain size on the amphiphilic behaviour of poly(3-alkyl-1-vinylimidazolium) bromide in aqueous medium

Several 3-alkyl-1-vinylimidazolium bromides differing by the length of the alkyl chain were prepared and polymerized using a free radical route. The behaviour of the obtained homopolymers in aqueous medium was investigated by several physico-chemical methods including viscosimetry, surface tension measurements and fluorescence spectroscopy. These experiments highlighted a strong influence of the length of the pendent alkyl chain on the side-chain aggregation tendency which is a property of such amphiphilic comb polymers. Fluorescence experiments were also conducted on the surface active analogues, in order to compare their behaviour to that of the polymers.

Nanoscale clustering of RGD peptides at surfaces using Comb polymers. 1. Synthesis and characterization of Comb thin films.

Theoretical and experimental studies were conducted to elucidate the structure and properties of amphiphilic comb polymer thin films presenting nanoscale clusters of Arg-Gly-Asp (RGD) peptides for control of cell adhesion on biomaterials. Combs comprised of a poly(methyl methacrylate) backbone and short poly(ethylene oxide) side chains were synthesized, and peptides were tethered to the side chain ends to create nanoscale peptide clusters. In thin films, comb polymers containing >or = 30 wt % six to nine unit PEO side chains completely resisted adhesion of a model fibroblast cell line in the presence of 7.5% serum over 24 h. These same polymers modified with RGD peptides elicited tunable cell adhesion when mixed with unmodified combs in varying proportion. A self-consistent field lattice model of the interface between comb polymer films and water predicts an organization of the top molecular layer of comb polymer with the backbone oriented parallel to the interface in quasi-two-dimensional confinement and hydrophilic side chains extended in a brushlike layer into solution. This picture of a quasi-2D configuration is consistent with the observed surface properties of comb films in water as well as measurements of the RGD cluster density on mixed comb surfaces using fluorescent nanosphere labeling of ligand clusters.

Preparation of Protein-Resistant Surfaces on Poly(vinylidene fluoride) Membranes via Surface Segregation

Self-organizing blends of an amphiphilic comb polymer having a poly(methyl methacrylate) (PMMA) backbone and poly(ethylene oxide) (PEO) side chains in poly(vinylidene fluoride) (PVDF) have been examined as a means to create foul-resistant, self-healing surfaces on polymer membranes. X-ray photoelectron spectroscopy (XPS) analysis of phase inversion membranes prepared from these blends indicates substantial surface segregation of the amphiphilic component, which occurs both during the coagulation step of the phase inversion process and in subsequent annealing of the membranes in water. With annealing, a near-surface coverage of nearly 45 vol % comb polymer is produced on a membrane with a bulk comb concentration of only 3 vol %. Surface enrichment of the hydrophilic comb polymer is shown to impart significant resistance to the adsorption of bovine serum albumin (BSA). XPS analysis of membranes treated with concentrated acid shows that hydrophilic surface layers removed by acid exposure may be regenerated b...

Universal Multifunctional Initiator Containing Orthogonal Reactive Sites. Synthesis of Macromonomers and Comb Polymers Using Consecutive Controlled Free Radical and Cationic Ring-Opening Polymerizations

A multifunctional reagent (1) containing orthogonal reactive sites that could serve as an initiator for multiple living polymerizations, namely, controlled free radical, anionic, and cationic polymerizations, and a source for a variety of macromonomers, including those for condensation polymerization and functional polymers, has been designed and synthesized in three steps in good yields. The reagent contained an alkoxyamine derived from 2,2,6,6-tetramethylpiperidin-1-yloxyl (TEMPO), an oxazoline, and a protected hydroxyl group. Thus, initiation of controlled free radical polymerization of styrene at the alkoxyamine terminal gave a polystyrene (PS) macromonomer with low polydispersity (Mw/Mn = 1.06−1.16). Cationic ring-opening polymerization of the oxazoline group gave an amphiphilic comb polymer with a hydrophilic poly(ethyleneimine) backbone and a hydrophobic PS side chain. The polymers were characterized by GPC, 1H and 13C NMR, and MALDI−TOF mass spectroscopy. The versatility of the structure is such that different types of macromonomers and macroinitiators suitable for many of the major methods of polymer synthesis can be made, making 1 a “universal” initiator.

Synthesis and characterization of amphiphilic comb-polymers via ring-opening metathesis polymerization of exo,exo-5,6-bis(alkoxymethyl)-7-oxabicyclo[2.2.1]hept-2-enes

A number of exo,exo-5,6-bis(alkoxymethyl)-7-oxabicyclo[2.2.1]hept-2-enes (exo,exo-5,6-bis(alkoxymethyl)-7-oxanorbornenes) with long alkyl chains were prepared by reduction of the Diels-Alder adduct of furan and maleic anhydride, followed by alkylation with a series of different n-alkylbromides. These monomers were polymerized via ring-opening metathesis polymerization (ROMP) catalyzed by ruthenium trichloride in ethanolic solution. Contrary to a helical conformation as it was predicted by a previous molecular model study the poly(7-oxanorbornenes) adopt a coil conformation in solution. In bulk the materials show side chain crystallization.

Chromatography of amphiphilic graft copolymers

AbstractAmphiphilic comb polymers were prepared through grafting poly(ethylene glycol) methyl ether (MPEG 2000) onto acrylic and methacrylic copolymers. The graft copolymers were purified from unreacted MPEG by partition chromatography on methanol pretreated fibrous cellulose using ethyl acetate and methanol as eluents. The separation was found to depend on the water contents of the cellulose and the eluents. It is proposed that one parameter of importance for the chromatographic separation is the formation of hydrated inverted micelles. The amphiphilic comb polymers were shown by gel chromatography on Sepharose to form high molecular weight aggregates in water. On addition of sodium lauryl sulphate or inorganic salts to the eluent at low ionic strengths these aggregates dissociated and were fractionated by the gel. It was also shown that on GPC in THF solution on Styragel columns the polymers exhibited apparent molecular weights equal or smaller than those of the corresponding backbones. This effect may be a consequence of the graft copolymers having relatively small hydrodynamic volumes, and this idea is supported by the fact that their intrinsic viscosities generally were lower than those of the backbones. However, adsorption on the Styragel columns also may be of importance.